Electrostatic grids

ABSTRACT

An electrostatic grid, especially useful in a flocking machine, has an exposed portion providing a corona which prevents flock from accumulating on the grid.

1451 Feb. 15,1972

United States Patent Corneau [s4] ELECTROSTATIC GRIDS Walsh et a1. 3,379,175 4/1968 Spencer........... [72] Inventor: George E. Corneau, Central Falls, R.1. 2,976,839 311% okma et [73] Assignee: lndev,Inc.,Pawtucket,R.1. 2,742,018 4/1956 Lindquist..... 221 Filed:, Aug. 5, 1970 [21] Appl.No.: 61,056

Primary Examiner- MerVinIStein Assistant Examiner-Leo Millstein Anamey-W. R. Hulbert [s2] u.s.c1..............................118/624, 118/621, 118/627,

Answer ch prevents 623, 624, v 640; 1 17/17 An electrostatic gi'id,especia1ly useful in a flocking machine, Rdennces Cited has an exposed portron prov1d1n g a corona wh1 flock from accumulatlng on the gnd. I UNITED STATES PATENTS I 3,530,828 9/1970 Schwartz s1 1m.c1,.. [58] Fieldo1'Search..........;.......

118/624 scm wnwm n nm PAIENIEUFEB 15 m2 SHEET 3 (IF 3 ELECTROSTATIC GRIDS This invention relates to particle orientation and deposition, and particularly to flocking.

It is an object of this invention to improve flock orientation and distribution in flocking apparatus simply, efficiently, and economically, with structures utilizable in conventional flocking apparatus.

Another object is to provide improved electrostatic grids and grid systems for particle-depositing apparatus, such as flocking machines, so as to produce improved flocked articles of predetermined controlled fiber density and distribution.

Another-object is to reduce clinging of particles, such as flock fiber, to electrostatic grids and diminish or prevent particleaccumulation on these grids.

In one aspect, the invention features, in a flocking apparatus including a flock distributor for distributing flock fibers onto an article travelling through an electrostatic field in the apparatus, an electrically conductive grid element for providing the electrostatic field, the grid element being mounted between the distributor and the article with its longitudinal axis'transverse to the article, and comprising an electrically conductive member, connected to a source of electrical power, and a housing of electrical insulating material sized to expose only the portion of the conductive member disposed adjacent the distributor and to enclose the remainder of the conductive member, whereby a corona is formed adjacent the exposed portion of the grid element to prevent flock deposi tion thereon in the vicinity of the exposed portion.

In another aspect, a plurality of grid elements, each having an electrically conductive member and a housing of insulating material with converging sidewalls, arranged substantially in parallel and spaced from one another to provide flock flow passages therebetween from the distributor to the article, are rotatably mounted between opposed supporting members for rotation about a longitudinal axis, and reciprocating means is secured to each said grid element for rotating the grid elements in unison about these axes such that the converging sidewalls become periodically at least perpendicular to the article.

In a preferred embodiment, the grid housing is of teardrop configuration, having a rounded shape opposite the converging sidewalls; the flocking apparatus includes a plurality of oscillating members mounted beneath the article to impart localized vibrations to the article and the grid elements are arranged with alternate grid elements located directly adjacent one of these oscillating members, and the remaining grid elements located between adjacent oscillating members; the converging housing sidewalls include an angle of at most 90; the conductive metallic element is formed of an integral flexible metallic sheet shaped to conform to the inner surface of said housing, and has edges converging toward one another near the point of convergence of the housing sidewalls, with at least one converging metallic edge being exposed between the converging housing sidewalls; and, the insulating housing is sized to extend past both ends of the metallic element, and the grid member includes a solid plug of insulating material within the housing adjacent each end of the metallic element to prevent coronas at those ends.

Other objects, features, and embodiments will appear to one skilled in the art from the following description of a preferred embodiment of the invention, taken together with the attached drawings thereof, in which:

FIG. 1 is a side elevational view, partially broken away, of a flocking apparatus including a preferred embodiment of the present invention;

FIG. 2 is a perspective view of a preferred grid embodiment of this invention, shown with portions of grid mounting structure broken away;

FIG. 3 is a schematic sectional view of a series of grids and mounting structure therefor embodying this invention; and

FIG. 4 is a schematic sectional view illustrating operation of a grid constructed in accordance with this invention.

FIG. 1 shows a flocking apparatus having opposed end walls 11a, 1 lb, and which includes cyclone 12 which feeds disvso as to provide a textured surface, which will tributor 14 (e.g., an elongated perforated trough extending the width of the article to be flocked andmeans, such as arotary brush, for feeding flock through the perforations therein, such as shown in US. Pat. No. 3,426,729) for feeding'flock into flocking chamber '16 onto the article I7 to be flocked. A

rubberized blanket 20 is anchored to plate 22 atentrance 23 to the flocking apparatus, and to-plate 24 at exit 26, and supports the article 17. Beater bars 28 (each havinga cylindrical mounted beneath the beater bars, and is connected by ducts,

as is suction clean-off nozzle 38, to return cyclone 40.

A plurality of grid elements 42 are rotatablymounted by nylon rods 63, 64 between crossbeams 45 and 46, so that alternate grids are aligned with a beater bar beneath and the other grid elements are located midway between two adjacent beater bar assemblies. The grids are equally spaced from one another along the direction of travel of the article beneath, and preferably extend across the entire width of the article.

Referring to FIGS. 2-4, each grid element is of general teardrop configuration, and includes an electroconductive metallic conductor 48, which is connected, by lead 50, to a source of high voltage (not shown), delivering a voltage sufficient to produce an electrostatic field for orienting the fibers, but not so intense as to are, e.g., across to walls 110 or 11b, or up to distributor l4 (e.g., on the order of 25,000 volts).

Conductor 48 is formed of an integral metal sheet, folded into a teardrop shape, and has a sharpened knife edge 5 I. Insulating housing 54 (advantageously formed of one-eighth inch flexible acrylic resin, such as Plexiglass G, manufactured by Rohm & Haas Co.) has converging sidewalls 55 (preferably including an angle of 90 or less), which expose knife edge 51 at the line of convergence of the walls. Housing 54 is advantageously of greater length than conductor 48, so as to separate the conductor from apparatus walls 11a, 11b. As shown in FIG. 2, each end of conductor 48 is sealed by a plug 57, which is formed of an electrical insulating material, such as an acrylic resin, to prevent corona at the ends of the conductor. The top edges 58, 59 of housing 54 may be adhered to one another (e.g., by heat sealing) adjacent the ends of conductor 48 to firmly support the exposed knife edge 51. The exposed outer surfaces of housing walls 55, if formed of a material having a smooth, glassy finish (such as the aforesaid Plexiglass"), are preferably roughened, such as by sanding,

have less tendency to attract flock particles. 2

A second end plug 60, also formed of insulating material (e.g., an acrylic resin) is wedged into each end of housing 54, and each has an opening 62, into which is tightly secured a supporting rod 63 or 64. Each rod 63 is rotatably secured in a crossbeam 45 which is secured to the near wall 11a of apparatus 10, whereas each rod 64 is rotatably secured in a crossbeam 46 which is secured to the far wall 11b of apparatus 10. Each link 72 has an opening 73 receiving rotatably therethrough a rod 64, and is rotatably secured to reciprocating bar 76. As shown in FIGS. 1 and 3, one end 80 of bar 76 is rotatably secured, through a coupling 81, to one end of a conventional fluid-driven (e.g., pneumatic) piston rod 82, located in a suitable fluid pressure cylinder 84. As shown in FIG. I,

. cylinder 84 is rotatably supported on mounting structure 88 which is mounted on apparatus 10.

In operation, the article 17 is introduced at entrance 23 and moved by appropriate means (not shown-e.g., a textile takeup roller) slideably along blanket 20 towards exit 26. Article 17 is precoated with a suitable adhesive, and, e.g., beater bars 28 are grounded to serve as a source of zero potential to the grid elements. Or, if the adhesive is itself conductive (e.g., a water-base adhesive) and is continuous over the article surface, the article itself may be grounded externally of and prior to entry to the flocking machine (by grounding the doctor blade applying the adhesive to the article, for instance). The

rotation of beater bars 28 causes longitudinal bars 30 to impart a vibratory movement to blanket 20, which aids in orienting the flock on the article along the lines of force provided by the electrostatic field. The flock is customarily precoated with a finishing agent to eliminate static changes thereon and increase responsiveness of the flock fibers to the electrostatic field.

When the grids are connected to a source of electrical potential, not only are electrostatic field force lines set up, as shown in FIG. 4, but further, the exposed edge 51 of each grid element causes a corona to be formed at the top of each grid. Flock fibers from distributor 14 fall to the article beneath and are adhesively bonded thereto. Excess flock from suction nozzle 38 is fed to cyclone 40, thence back to hopper 36, and thence back to cyclone 12 for redistribution.

As the flock fibers pass from the flock distributor to the article beneath, those falling between the adjacent grids will be oriented in the force field so as to line up with the force field, and hence will deposit substantially upright into the article. Additional grid elements downstream of the distributor further enhance the orientation process. The fibers which fall toward the grid, rather than contacting the grid, with subsequent clinging and accumulation of fibers thereon, are repelled by the corona, and hence enter the main stream of fiock flow between the grids. In general, the exposed portion of the grid should not be so large as to cause short circuiting,

or arcing, or so as to disturb the uniformity of the electrostatic field at the article.

In addition, even those fibers which do contact the grid walls are prevented from accumulation thereon. The reciprocation of bar 76 at a preferred speed in the range of 30 times per minute causes continuous fanning of the grid elements, thus continuously impelling any clinging fibers off the grid walls. As shown in figures, the fanning causes the opposed grid walls not only to reach perpendicularity with the article beneath but to exert a positive downward impelling force on the fibers. Furthermore, since the glassy grid walls have been sanded to replace the glassy finish with a texturized one, the walls are substantially nonattractive to flock fibers.

Other embodiments will occur to those skilled in the art and are within the following claims.

What is claimed is:

1. In a flocking apparatus including a flock distributor for distributing flock fibers to an article travelling through an electrostatic field in said apparatus,

an electrically conductive grid element for providing said electrostatic field mounted between said distributor and said article, with the longitudinal axis of said grid element transverse to said article,

said grid element comprising an electrically conductive member, connected to a source of electrical power, and a housing of electrical insulating material sized to expose only the portion of said conductive member disposed adjacent said distributor and to enclose the remainder of said member,

whereby a corona is formed adjacent the said exposed portion of said grid element to prevent flock deposition on said grid element.

2. The apparatus of claim 1 wherein said housing has converging sidewalls, and said conductive member is exposed between said converging sidewalls at the point of convergence of said sidewalls.

3. The apparatus of claim 2 including a plurality of said grid elements, arranged substantially in parallel, and spaced from one another to provide flock flow passages therebetween from said distributor to said article.

4. The apparatus of claim 3 including a plurality of oscillating members, arranged in parallel, mounted beneath said article to impart localized vibrations to said article as said article passes over each member, wherein said oscillating members and said grid elements each have their longitudinal axes arranged substantially perpendicular to the direction of travel of said article, and wherein said gridelements are arranged with alternate grid elements located directly adjacent one of said oscillating members, and the remaining grid elements located between adjacent oscillating members.

5. The apparatus of claim 3 wherein said apparatus includes mounting means .for said grid element 5 comprising opposed supporting members, one mounted on said apparatus on each side of said article, said members constructed to rotatably support said grid elements therebetween about a longitudinal axis of rotation, and reciprocating means secured to each said grid element for rotating said grid elements in unison about said axes.

6. The apparatus of claim 5 wherein said grid elements are arranged for sufficient rotation in each direction .to render each said converging said wall perpendicular to said article.

7. The apparatus of claim 5 wherein said grid element housing is of teardrop configuration, having a rounded portion oppositely located from said point of convergence, and is sized to extend past the ends of said metallic element,

said mounting means includes a rod protruding from each end of said housing at said rounded portion rotatably into one of said supporting members, and

said reciprocating means includes a reciprocating bar located adjacent one of said supporting members, a plurality of linking members, each secured at one end rotatably to one said rod and at the other end fixedly to said bar, and drive means for reciprocating said bar in a direction substantially perpendicular to said grid elements, so as to rotate said grid elements on said rods alternately in opposite directions.

8. In a flocking apparatus including a flock distributor for distributing flock fibers to an article travelling through an electrostatic field'in said apparatus,

a plurality of electrically conductive grid elements for providing said electrostatic field mounted between said distributor and said article, said elements arranged substantially in parallel, with the longitudinal axis of said elements transverse to said article, and said elements spaced apart from one another to provideflock flow passages therebetween from said distributor to said article,

each said grid element comprising an electrically conductive member, connected to a source of electrical power, and a housing of electrical insulating material having converging sidewalls, the point of convergence of said sidewalls being located opposite said flock distributor,

mounting means for said grid elements comprising opposed su ortin members, one mounted on said a aratus on.

each side of said article, said members constructed to rotatably support said grid elements therebetween about a longitudinal axis of rotation, and

reciprocating means secured to each said grid element for rotating said grid elements in unison about said axes,

said grid elements being arranged for sufficient rotation in each direction to render each said converging sidewall perpendicular to said article.

9. The apparatus of claim 8 wherein said grid elements housing is of tear drop configuration, having a rounded portion oppositely located from said point of convergence,

said mounting means includes a rod protruding from each end of said housing at said rounded portion rotatably into one of said supporting members, and

said reciprocating means includes a reciprocating bar located adjacent one of said supporting members, a plurality of linking members, each secured at one end rotatably to one said rod and at the other end fixedly to said bar, and drive means for reciprocating said bar in a direction substantially perpendicular to said grid elements, so as to rotate said grid elements on said rods alternately in opposite directions. 

1. In a flocking apparatus including a flock distributor for distributing flock fibers to an article travelling through an electrostatic field in said apparatus, an electrically conductive grid Element for providing said electrostatic field mounted between said distributor and said article, with the longitudinal axis of said grid element transverse to said article, said grid element comprising an electrically conductive member, connected to a source of electrical power, and a housing of electrical insulating material sized to expose only the portion of said conductive member disposed adjacent said distributor and to enclose the remainder of said member, whereby a corona is formed adjacent the said exposed portion of said grid element to prevent flock deposition on said grid element.
 2. The apparatus of claim 1 wherein said housing has converging sidewalls, and said conductive member is exposed between said converging sidewalls at the point of convergence of said sidewalls.
 3. The apparatus of claim 2 including a plurality of said grid elements, arranged substantially in parallel, and spaced from one another to provide flock flow passages therebetween from said distributor to said article.
 4. The apparatus of claim 3 including a plurality of oscillating members, arranged in parallel, mounted beneath said article to impart localized vibrations to said article as said article passes over each member, wherein said oscillating members and said grid elements each have their longitudinal axes arranged substantially perpendicular to the direction of travel of said article, and wherein said grid elements are arranged with alternate grid elements located directly adjacent one of said oscillating members, and the remaining grid elements located between adjacent oscillating members.
 5. The apparatus of claim 3 wherein said apparatus includes mounting means for said grid element s comprising opposed supporting members, one mounted on said apparatus on each side of said article, said members constructed to rotatably support said grid elements therebetween about a longitudinal axis of rotation, and reciprocating means secured to each said grid element for rotating said grid elements in unison about said axes.
 6. The apparatus of claim 5 wherein said grid elements are arranged for sufficient rotation in each direction to render each said converging said wall perpendicular to said article.
 7. The apparatus of claim 5 wherein said grid element housing is of teardrop configuration, having a rounded portion oppositely located from said point of convergence, and is sized to extend past the ends of said metallic element, said mounting means includes a rod protruding from each end of said housing at said rounded portion rotatably into one of said supporting members, and said reciprocating means includes a reciprocating bar located adjacent one of said supporting members, a plurality of linking members, each secured at one end rotatably to one said rod and at the other end fixedly to said bar, and drive means for reciprocating said bar in a direction substantially perpendicular to said grid elements, so as to rotate said grid elements on said rods alternately in opposite directions.
 8. In a flocking apparatus including a flock distributor for distributing flock fibers to an article travelling through an electrostatic field in said apparatus, a plurality of electrically conductive grid elements for providing said electrostatic field mounted between said distributor and said article, said elements arranged substantially in parallel, with the longitudinal axis of said elements transverse to said article, and said elements spaced apart from one another to provide flock flow passages therebetween from said distributor to said article, each said grid element comprising an electrically conductive member, connected to a source of electrical power, and a housing of electrical insulating material having converging sidewalls, the point of convergence of said sidewalls being located opposite said flock distributor, mounting means for said grid elements comprising opposed supporting members, one mounted on said apparatus on each side of said artiCle, said members constructed to rotatably support said grid elements therebetween about a longitudinal axis of rotation, and reciprocating means secured to each said grid element for rotating said grid elements in unison about said axes, said grid elements being arranged for sufficient rotation in each direction to render each said converging sidewall perpendicular to said article.
 9. The apparatus of claim 8 wherein said grid elements housing is of tear drop configuration, having a rounded portion oppositely located from said point of convergence, said mounting means includes a rod protruding from each end of said housing at said rounded portion rotatably into one of said supporting members, and said reciprocating means includes a reciprocating bar located adjacent one of said supporting members, a plurality of linking members, each secured at one end rotatably to one said rod and at the other end fixedly to said bar, and drive means for reciprocating said bar in a direction substantially perpendicular to said grid elements, so as to rotate said grid elements on said rods alternately in opposite directions. 